Gardeners who deadhead their dahlias regularly through autumn can keep the flowers blooming longer, according to the Royal Horticultural Society (RHS).
Dahlias are among the most striking garden flowers, adding bold colours to borders as summer blooms fade. Their wide variety of shapes, colours and sizes suits almost any garden, including containers and borders.
Unlike many flowers, dahlias can continue flowering well into autumn and are especially valuable for extending colourful displays later in the year. The RHS says they can bloom through to the first frosts, making them one of the best plants for prolonging the flowering season.
How to deadhead dahlias
Removing spent blooms encourages more flowers, even as the weather turns colder. This is particularly useful at the end of September, when dahlias can still be putting on an impressive display.
Deadheading is the term for removing faded or dead flowers, according to the RHS. It is done to keep plants “looking attractive” and to “encourage more blooms”.
The RHS recommends cutting back to a leaf joint lower down the stem rather than simply removing the flower head. To identify a spent flower, look for blooms that have faded, wilted or lost their fresh appearance, then follow the flower stem down towards the foliage.
Distinguishing buds from spent flowers
There is a useful tip for telling a spent dahlia flower from a new bud. According to the RHS, flower buds tend to be rounded, whereas spent flowers are more pointed once their petals have dropped.
Dahlias are not hardy and will be damaged by freezing temperatures. Once the foliage has been damaged by the first frosts, gardeners can either leave the tubers in the ground or lift and store them in a frost-free place over the winter months.
Gardeners in milder parts of the UK with light, free-draining soil can choose to leave them in the ground, but this carries a greater risk of winter losses. Deadheading is not the only way to encourage more blooms—if you have plenty of flowers, dahlias also make excellent cut flowers for indoors.
